1. Field of the Invention
The present invention relates to a microprocessor controlled camless internal combustion engine that contains a plurality of digitally latched solenoid control valves that control a number of hydraulically driven valves and fuel injectors.
2. Description of Related Art
Conventional compression ignition engines contain cams that coordinate the timing of the intake and exhaust valves with the pistons and fuel injectors of the engine. Cams are subject to wear which may affect the timing of the valves. Additionally, cams are not readily susceptible to changes in the valve timing.
U.S. Pat. No. 5,125,370 issued to Kawamura; U.S. Pat. No. 4,715,330 issued to Buchl and U.S. Pat. No. 4,715,332 issued to Kreuter disclose various camless solenoid actuated intake and exhaust valves. The valve stems are magnetically coupled to the solenoids which move the valves between open and closed positions. The mass and inertia of the intake/exhaust valves require energy to move the valves. This power requirement reduces the energy efficiency of the engine. Additionally, the response time for opening and closing the valves is relatively slow, thereby reducing the control of the valve.
U.S. Pat. Nos. 5,248,123, 5,022,358 and 4,899,700 issued to Richeson; U.S. Pat. No. 4,791,895 issued to Tittizer and U.S. Pat. No. 5,255,641 issued to Schechter all disclose hydraulically driven intake/exhaust valves. The hydraulic fluid is typically controlled by a solenoid control valve. The solenoid control valves described and used in the prior art require a constant supply of power to maintain the valve in an actuating position. The constant supply of power again consumes more energy from the engine. Additionally, the solenoid control valves of the prior art have been found to be relatively slow thus restricting the accuracy of the valve timing.
U.S. Pat. Nos. 4,200,067 and 4,206,728 issued to Trenne; and U.S. Pat. No. 5,237,968 issued to Miller et al. disclose hydraulic systems that control the injection of fuel and the timing of valves. These systems incorporate a cam or spool that controls the working fluid which drives the fuel injector and the valves. The components are coupled together so that fuel injection and valve movement always occur in the same time sequence. It sometimes desirable to vary the movement and timing of the fuel injector and the valves. For example, when decelerating a vehicle, it is desirable to brake the engine by allowing the pistons to continually compress air during the power strokes of the engine, an engine mode commonly referred to as Jake braking. Jake braking requires a cessation of fuel injection during the expansion stroke of a CI engine. Additionally, the exhaust valve is typically slightly opened when the piston reaches top dead center of the compression stroke.
U.S. Pat. No. 5,117,790 issued to Clarke et al. discloses a valve/fuel injection system which contains a separate actuator for each valve and fuel injector of the engine. The actuators are controlled by a central microprocessor. The Clarke system is thus capable of running the engine in different modes such as Jake braking. Clarke is silent as to the actual implementation of the actuators and the valves that control the actuators. It is not apparent whether Clarke provides a responsive, energy efficient camless engine that can operate in a variety of modes. It would be desirable to provide an accurate, responsive, energy efficient camless internal combustion engine than can operate in different modes.
Fuel injectors of the prior art typically contain an hydraulically driven intensifier that increases the pressure of the fuel that is ejected into the internal combustion chamber. The hydraulic fluid is provided by a pump that is driven by the engine. To compensate for variations in engine temperature, rpm's, and other factors the hydraulic system typically contains a pressure relief valve that opens when the rail pressure exceeds a predetermined value. The pressure relief valve contains a spring that biases the valve into a closed position. The pump must generate work to overcome the force of the spring during a by-pass cycle. The additional work increases the frictional horsepower and reduces the fuel efficiency of the engine. It would be desirable to provide a hydraulic by-pass system that would not require work from the pump.